Suppression of Low-mass Galaxy Formation around Quasars at z~2-3

Abstract

We have carried out deep and wide field imaging observations with narrow bands targeting 11 quasar fields to systematically study the possible photoevaporation effect of quasar radiation on surrounding low mass galaxies at $z\sim2-3$. We focused on Lyman alpha emitters (LAEs) at the same redshifts as the quasars that lie within the quasar proximity zones, where the ultra-violet radiation from the quasars is higher than the average background at that epoch. We found that LAEs with high rest-frame equivalent width of Ly$\alpha$ emission ($EW_0$) of $\gtrsim 150$\AA$~$ with low stellar mass ($\lesssim 10^8 M_{\odot}$), are predominantly scarce in the quasar proximity zones, suggesting that quasar photoevaporation effects may be taking place. The halo mass of LAEs with $EW_0>150$\AA$~$ is estimated to be $3.6^{+12.7}_{-2.3}\times10^9 M_{\odot}$ either from the Spectral Energy Distribution (SED) fitting or the main sequence. Based on a hydrodynamical simulation, the predicted delay in star formation under a local UV background intensity with $J (\nu_L)\gtrsim10^{-21}$ erg s$^{-1}$ cm$^{-2}$ Hz$^{-1}$ sr$^{-1}$ for galaxies having less than this halo mass is about $>20$ Myr, which is longer than the expected age of LAEs with $EW_0>150$\AA. On the other hand, the photoevaporation seems to be less effective around very luminous quasars, which is consistent with the idea that these quasars are still in an early stage of quasar activity.